1. Field of the Invention
The present invention relates to a refrigerant compressor used for an automotive air-conditioning system. More particularly, the present invention relates to shapes of suction holes and discharge holes provided in a valve plate of a compressor.
2. Description of the Related At
A description of the structure and operation of a refrigerant compressor for an automotive air conditioning system follows. Referring to FIG. 1, a conventional compressor 100 is depicted. Compressor 100 comprises front housing 30, housing 27, valve plate 1, and rear housing 32. Along the central axis of compressor 100 is provided a drive shaft 34, which is supported rotatably by needle bearings 35 and 36. Within housing 27, cam rotor 37 which is fixed to drive shaft 34 engages the inner wall of front housing 30 via thrust bearing 38. Cam rotor 37 rotates when drive shaft 34 is rotated. Hinge mechanism 39 couples cam rotor 37 with inclined plate 40. Inclined plate 40 rotates with cam rotor 37. Wobble plate 43 engages with inclined plate 40 via thrust bearing 41 and needle bearing 42. A wobbling motion is induced in inclined plate 40, so that inclined plate 40 wobbles while rotating. This motion of inclined plate 40 transfers to wobble plate 43. Rotation of wobble plate 43 is inhibited by engagement with a guide bar 44. Therefore, only the wobbling component of the motion of inclined plate 40 is transferred from inclined plate 40 to wobble plate 43. Wobble plate 43 has a wobbling motion, but does not rotate with drive shaft 34. Rod 45 is connected by spherical coupling to wobble plate 43 and to a plurality of pistons 46. When wobble plate 43 wobbles, each of pistons 46 reciprocates in one of a plurality of cylinders 71.
Suction valve reed 22, discharge valve reed 2, and valve retainer 3 are fixed by bolt 47 to valve plate 1. Suction holes 5 and discharge holes 4 correspond to each piston cylinder 71. Suction chamber 72 and discharge chamber 70 are formed by valve plate 1 and the rear housing 32, and are separated by inside partition plate 33.
When drive shaft 34 is rotated by an external power source (not shown), each piston 46 reciprocates in its respective piston cylinder 71. When piston 46 is moving leftward in FIG. 1, the suction phase is executed, and when piston 46 is moving rightward, the compression phase is executed.
In the suction phase, refrigerant gas in suction chamber 72 is drawn into piston cylinder 71 through suction hole 5. Due to the pressure variance between suction chamber 72 and piston cylinder 71, the refrigerant gas in suction chamber 72 flows to suction hole 5, passes through suction hole 5, opens suction valve reed 22, and enters piston cylinder 71. Suction valve reed 22 prohibits a reverse flow of refrigerant gas into suction chamber 72 during the compression phase.
In the compression phase, the refrigerant gas in piston cylinder 71 is discharged into discharge chamber 70 through discharge hole 4. Due to the pressure variance between piston cylinder 71 and discharge chamber 70, the refrigerant gas passes through discharge hole 4, opens discharge valve reed 2, and enters discharge chamber 70. Discharge valve reed 2 prohibits a reverse flow of the refrigerant gas into piston cylinder 71 during the suction phase.
FIG. 2a depicts a cross-sectional view of valve plate 1 from the rear housing side of valve plate 1. FIG. 2b depicts a cross-sectional view of valve plate 1 from the cylinder head side of valve plate 1. With reference to FIG. 2a, rear housing 32 is fixed to housing 27 by a plurality of bolts 130. Suction holes 5 and discharge holes 4 are disposed equiangularly around the center CO and correspond to piston cylinders 71. Suction chamber 72 and discharge chamber 70 are separated by inside partition plate 33. Discharge valve reed 2 within inside partition plate 33 is substantially star-shaped. The arms of discharge valve reed 2 cover discharge holes 4. With reference to FIG. 2b, suction valve reed 22 also is substantially star-shaped. Within each arm, a hole 22h enables the discharge gas to flow therethrough.
FIG. 3 depicts valve plate 1 as viewed from the side of valve plate 1 facing discharge chamber 70. Discharge holes 4 and suction holes 5 are disposed equiangularly with respect to the center C of valve plate 1. FIG. 4 and FIG. 5 are corresponding radial, cross- sectional views of valve plate 1 of FIG. 1. Valve reed 2 is fixed between valve plate 1 and valve retainer 3. Discharge holes 4 have side walls which are substantially perpendicular to the opposing surfaces of valve plate 1.
FIG. 4 and FIG. 5 depict valve plate 1 during the compression phase. When the refrigerant gas is discharged from cylinders 71, it strikes, pushes, and displaces valve reed 2. The refrigerant gas flows into discharge chamber 70 through a gap created between valve reed 2 and valve plate 1. When refrigerant gas flow impinges against reed valve 2 in FIG. 4, its flow path may be diverted at an angle substantially perpendicular to valve plate 1. Turbulence in the refrigerant gas flow may be created due to the abrupt change in the direction of flow. Further, a portion of the refrigerant gas flow impinging against valve reed 2 may not enter discharge chamber 70, and may instead return to piston cylinder 71. These turbulence effects are indicated by the arrows in FIG. 4 and FIG. 5. Therefore, turbulence of the refrigerant gas flow may result in flow resistance at discharge hole 4. Such flow resistance lowers the volumetric efficiency, a primary measure of the performance of compressor 100. The turbulence of flow also disturbs the motion of valve reed 2 and impedes valve reed 2 from discretely and completely opening and closing. Moreover, the turbulence of flow in discharge holes 4 may cause noise in compressor 100. Similar problems may occur with respect to suction holes 5.
Thus, it has long been desired to resolve effectively the problem of the turbulence of refrigerant gas flowing through the suction holes and discharge holes and to suppress noise generated thereby.